1. Field of the Invention
The present invention relates to a thermoelectric conversion element and a thermoelectric conversion module. Specifically, the present invention relates to a thermoelectric conversion element and a thermoelectric conversion module, which have excellent mechanical strength and thermoelectric conversion performance, and to methods for manufacturing the thermoelectric conversion element and the thermoelectric conversion module.
2. Description of the Related Art
Thermoelectric conversion materials that enable the interconversion between heat energy and electric energy are used in a thermoelectric conversion element such as a power generating element for thermally generating electric power or a Peltier element.
The thermoelectric conversion element can directly convert heat energy into electric power and thus has an advantage of not requiring a moving part. Therefore, by providing a power generating device using the thermoelectric conversion element in a heat exhaust site such as an incinerator or various factory facilities, it is possible to obtain electric power in a simple manner without needing to incur operational costs.
Regarding the thermoelectric conversion element, as a thermoelectric conversion material demonstrating excellent thermoelectric conversion performance, a carbon nanotube is known. In the following description, the carbon nanotube will be referred to as CNT as well.
For example, WO2012/121133A describes a thermoelectric conversion material which is formed of holes and a flexible organic material containing dispersed fine CNT particles and in which a mass ratio of CNT with respect to the organic material is 50% to 90% by mass.
Furthermore, WO02012/121133A describes a thermoelectric conversion module including a plurality of thermoelectric conversion elements in which the thermoelectric conversion material is used as a thermoelectric conversion layer and the thermoelectric conversion layer is interposed between electrodes that come into contact with the upper and lower portions of the thermoelectric conversion layer. In the thermoelectric conversion module, the plurality of thermoelectric conversion elements is arranged on a film substrate, and the upper electrode of a thermoelectric conversion element is connected to the lower electrode of an adjacent thermoelectric conversion element such that the plurality of thermoelectric conversion elements is connected to each other in series.
Incidentally, as described in WO2012/121133A, the thermoelectric conversion element is generally constituted with an electrode disposed on a plate-like substrate, a block-like thermoelectric conversion layer (power generating layer) disposed on the electrode, and a plate-like electrode disposed on the thermoelectric conversion layer. The thermoelectric conversion element having such a configuration is also called uni leg-type thermoelectric conversion element.
That is, in a general thermoelectric conversion element, the thermoelectric conversion layer is interposed between the electrodes in a thickness direction, and a temperature difference is caused in the thickness direction of the thermoelectric conversion layer, thereby converting heat energy into electric energy.
In contrast, JP3981738B describes a thermoelectric conversion element using a substrate having a high thermal conduction portion, in which heat energy is converted into electric energy by causing a temperature difference in the plane direction of a thermoelectric conversion layer, not in the thickness direction of the thermoelectric conversion layer.
Specifically, JP3981738B describes a thermoelectric conversion element having a constitution in which a flexible film substrate constituted with two kinds of materials having different thermal conductivities is disposed on both surfaces of a thermoelectric conversion layer formed of a P-type material and an N-type material, and the materials having different thermal conductivities are positioned on the outer surface of the substrate and in a direction perpendicular to a direction along which electricity is conducted.